Remove all native alert()/confirm() calls

Native confirm() dialogs block browser automation entirely (discovered
via a frozen tab while browser-testing the app.messages/app.modal
adoption), and native alert()/confirm() are visually inconsistent with
the rest of the UI. Replaced every call site with
app.messages.action/confirm/toast:

- directory.ejs: rotateSecret/deleteResource confirms and all inline
  save/add/remove-group/edge error alerts now target #resourceModal's
  actionMessage (or, for deleteResource — called from the outer table
  row, not the modal — the page's own card).
- impersonate_modal.ejs, onboarding.ejs: no local .actionMessage target
  exists on these pages, so their alerts became page-wide toasts.
- executive.ejs: two alerts in sendNotification's validation now use the
  existing $compose target; saveTos's alert now reuses the function's
  own msgEl inline-message element instead of introducing a second
  mechanism.
- users.ejs, profile.ejs, proxy's profile.ejs: toggleActive's alert
  (no row context available at the call site) became a toast;
  revokeInvite/revokeToken/rotateToken use the row/card element already
  in scope.
- app.js: removed app.user.remove and app.oauthClient.remove, which
  contained native confirm() guards and had zero callers anywhere in the
  app — dead code, deleted rather than converted.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

nodejs/views/executive.ejs

@@ -117,8 +117,8 @@
 		const msgEl       = document.getElementById('notif-result');
 		const $compose    = $('#notif-subject').closest('.card-body');
 
-		if (!subject || !message) { alert('Subject and message are required.'); return; }
-		if (!filterCheck) { alert('Choose who to send this to.'); return; }
+		if (!subject || !message) { app.messages.action('Subject and message are required.', $compose, 'danger'); return; }
+		if (!filterCheck) { app.messages.action('Choose who to send this to.', $compose, 'danger'); return; }
 		const filterType = filterCheck.value;
 
 		let filter_value = '';
@@ -179,7 +179,12 @@
 		const resetAcceptance = document.getElementById('tos-reset-acceptance').checked;
 		const msgEl = document.getElementById('tos-result');
 
-		if (!content) { alert('Terms of Service text cannot be empty.'); return; }
+		if (!content) {
+			msgEl.className = 'alert alert-danger mt-2';
+			msgEl.textContent = 'Terms of Service text cannot be empty.';
+			msgEl.style.display = '';
+			return;
+		}
 
 		app.tos.update({content, resetAcceptance}, function(error, data) {
 			if (error) {